With the development of the future service, next generation wireless communication systems, such as 3GPP (third Generation Partnership Project) LTE (long term evolution), WiMAX (World Interoperability for Microwave Access) and IMT-A (International Mobile Telecommunications-Advanced) system etc. are introduced to satisfy the QoS (Quality of Service) of various services. However, another challenge becomes evident: the increasing power consumption of the mobile device and the battery capacity does not keep pace with the increasing demand for energy to handle the upcoming tasks.
To overcome the aforementioned drawbacks, cellular controlled D2D communication systems are introduced.
Cellular controlled D2D communication can be seen as one complementary for the conventional cellular communication systems, and is compatible to any cellular communication technology e.g. GSM, UMTS, 3GPP LTE, WiMAX, or IMT-A etc. Compared with conventional cellular communication systems, cellular controlled D2D systems have the following advantages: power saving, capacity improvement and lower service cost etc for UE perspective, higher revenue, larger market penetration and new services for network provider, higher revenue, service scalability for service provider, low and energy saving for device manufacture.
More particular, cellular controlled D2D communication refers to a kind of D2D communication in which the traffic are transmitted directly between the terminal devices such as user equipments, while the traffic transmission is controlled by cellular network nodes such as eNBs (evolved Node B). For example, in a cellular controlled D2D communication, the random access, authorization, resource provision, and charging etc. are controlled by eNBs. In addition, the D2D communication with semi-distributed scheduling (which means D2D has limited scheduling ability under eNB's supervision) also belongs to cellular controlled D2D communication.
However, there exist some problems to be solved in the conventional cellular controlled D2D communication system. FIG. 1 shows such a scenario, wherein the geographical location of the participators (such as UE (User Equipment) 1 and UE2) intended to establish a cellular controlled D2D communication therebetween are very close, and the participators even know the situation each other, e.g. they are face to face in the same meeting room. For conventional cellular communication system, all the UEs are only communicated with eNB and they can't communicate directly. To apply D2D communication, according to the conventional cellular controlled communication, the channel quality between UEs should be in addition measured and feedback to eNB, so that the eNB can decide whether or not the situation is feasible to set up the cellular controlled D2D communication between UE1 and UE2. However, there is a fact that the participators (such as UE1 and UE2) know the situation relating to the channel quality better than the eNB. The measurement and feedback for D2D setup resulting in large latency and resource waste seem to be redundant in the above scenario.
From this issue, it may be desirable to provide a solution to take advantage of the pre-knowledge of the situation of the D2D participators to further speed up the D2D communication setup.